Battery-powered devices, such as cell phones, personal digital assistants (PDAs), MP3 players, and the like, often include a switching power supply to translate a voltage from a battery to a load, to provide a regulated voltage to the load as the battery voltage changes, or both. As the battery is depleted, its output voltage, called the battery voltage, tends to droop. A drooping battery voltage may cause the switching power supply to increase the current provided by the battery, called the battery current, to compensate. For some battery technologies, the battery current should not exceed a maximum battery current rating, which may include a maximum instantaneous battery current rating, a maximum average battery current rating, or both. Directly measuring battery current may be problematic since direct current (DC) current measurements often require a series element, which may add undesirable losses, complexity, or both. Thus, there is a need to estimate instantaneous battery current, average battery current, or both, of a battery that is used to power a switching power supply.